Web handling apparatus such as dryers for running webs usually include a closed housing forming one or more drying chambers or zones having a plurality of spaced nozzles, the nozzles usually arranged in an upper and lower array with a web running between them. The traveling web enters the housing through a narrow entrance slot, is acted on by gas (e.g., air) ejected from each of the nozzles, and then exits the housing through a discharge slot. The working air is usually supplied from an outside source or sources, is heated and is then supplied to the nozzles via headers, and the nozzles eject the air into the dryer chamber(s).
In web coating, printing and drying operations, it is often desirable that the web have contactless support, in order to avoid damage to the web itself or to the wet coating (such as ink) previously applied to one or more surfaces of the web. One conventional arrangement for contactlessly supporting a web during drying includes the aforementioned horizontal upper and lower sets of nozzles or air bars in a dryer between which the web travels. Hot air issuing from the air bars both dries and supports the web as it travels through the dryer. The dryer housing can be maintained at a slightly sub-atmospheric pressure by an exhaust blower or the like that draws off the moisture or other volatiles emanating from the web as a result of the drying of the water, coating or ink thereon, for example.
Manufacturers often produce products of varying width that require drying inside the dryer housing. Drying is a high energy use process and reducing the heated air flow inside the dryer for narrow width products may offer a quality improvement to the product and/or reduce energy use for the process by reducing the total heated air flow inside the dryer. However, accessing the interior of the dryer to modify the internals in an effort to optimize energy consumption is difficult and time-consuming. It also requires shutting down the dryer, which results in unnecessary downtime and production inefficiencies.
It therefore would be desirable to provide varying nozzle widths in a web handling apparatus housing without having to access the housing interior. It also would be desirable to do so while the unit continues to operate; e.g., “on the fly” without having to shut the unit down or temporarily pause operation, as well as providing safe operation of the unit.